Provided by: tio_3.9-1_amd64 
NAME
tio - a serial device I/O tool
SYNOPSIS
tio [<options>] <tty-device|profile|tid>
DESCRIPTION
tio is a serial device tool which features a straightforward command-line and configuration file
interface to easily connect to serial TTY devices for basic I/O operations.
OPTIONS
-b, --baudrate <bps>
Set baud rate [bps] (default: 115200).
-d, --databits 5|6|7|8
Set data bits (default: 8).
-f, --flow hard|soft|none
Set flow control (default: none).
-s, --stopbits 1|2
Set stop bits (default: 1).
-p, --parity odd|even|none|mark|space
Set parity (default: none).
Note: With mark parity the parity bit is always 0. With space parity the parity bit is always 1.
Not all platforms support mark and space parity.
-o, --output-delay <ms>
Set output delay [ms] inserted between each sent character (default: 0).
-O, --output-line-delay <ms>
Set output delay [ms] inserted between each sent line (default: 0).
--line-pulse-duration <duration>
Set the pulse duration [ms] of each serial port line using the following key value pair format in
the duration field: <key>=<value>
Each key represents a serial line. The following keys are available:
DTR Data Terminal Ready
RTS Request To Send
CTS Clear To Send
DSR Data Set Ready
DCD Data Carrier Detect
RI Ring Indicator
If defining more than one key value pair, the pairs must be comma separated.
The default pulse duration for each line is 100 ms.
-a, --auto-connect new|latest|direct
Automatically connect to serial device according to one of the following strategies:
new Automatically connect to first new appearing serial device.
latest Automatically connect to latest registered serial device.
direct Connect directly to specified TTY device.
All the listed strategies automatically reconnects according to strategy if device is not
available or connection is lost.
Default value is "direct".
--exclude-devices <pattern>
Exclude devices by pattern ('*' and '?' supported).
--exclude-drivers <pattern>
Exclude drivers by pattern ('*' and '?' supported).
--exclude-tids <pattern>
Exclude topology IDs by pattern ('*' and '?' supported).
-n, --no-reconnect
Do not reconnect.
This means that tio will exit if it fails to connect to device or an established connection is
lost.
-e, --local-echo
Enable local echo.
-t, --timestamp
Enable line timestamp.
--timestamp-format <format>
Set timestamp format to any of the following timestamp formats:
24hour 24-hour format ("hh:mm:ss.sss")
24hour-start 24-hour format relative to start time
24hour-delta 24-hour format relative to previous timestamp
iso8601 ISO8601 format ("YYYY-MM-DDThh:mm:ss.sss")
epoch Seconds since Unix epoch (1970-01-01)
Default format is 24hour
--timestamp-timeout <ms>
Set timestamp timeout value in milliseconds.
This value only takes effect in hex output mode where timestamps are only printed after elapsed
timeout time of no output activity from tty device.
Default value is 200.
-l, --list
List available targets (serial devices, TIDs, configuration profiles).
-L, --log
Enable log to file.
The log file will be automatically named using the following format tio_TARGET_YYYY-MM-
DDTHH:MM:SS.log. Target being the command line target such as tty-device, tid, or configuration
profile.
The filename can be manually set using the --log-file option.
--log-file <filename>
Set log filename.
--log-directory <path>
Set log directory path in which to save automatically named log files.
--log-append
Append to log file.
--log-strip
Strip control characters and escape sequences from log.
-m, --map <flags>
Map (replace, translate) characters on input to the serial device or output from the serial
device. The following mapping flags are supported:
ICRNL Map CR to NL on input (unless IGNCR is set)
IGNCR Ignore CR on input
IFFESCC Map FF to ESC-c on input
INLCR Map NL to CR on input
INLCRNL Map NL to CR-NL on input
IMSB2LSB Map MSB bit order to LSB on input
OCRNL Map CR to NL on output
ODELBS Map DEL to BS on output
ONLCRNL Map NL to CR-NL on output
OLTU Map lowercase characters to uppercase on output
ONULBRK Map nul (zero) to send break signal on output
OIGNCR Ignore CR on output
If defining more than one flag, the flags must be comma separated.
--input-mode normal|hex|line
Set input mode.
In normal mode input characters are sent immediately as they are typed.
In hex input mode bytes can be sent by typing the two-character hexadecimal representation of the
1 byte value, e.g.: to send 0xA you must type 0a or 0A.
In line input mode input characters are sent when you press enter. The only editing feature
supported in this mode is backspace.
Default value is "normal".
--output-mode normal|hex|hexN
Set output mode.
In hex mode each incoming byte is printed out as a 1 byte hex value.
In hexN mode, N is a number less than or equal to 4096 which defines how many hex values will be
printed before a line break.
Default value is "normal".
-c, --color 0..255|bold|none|list
Colorize tio text using ANSI color code value ranging from 0 to 255 or use "none" for no color or
use "bold" to apply bold formatting to existing system color.
Use "list" to print a list of available ANSI color codes.
Default value is "bold".
-S, --socket <socket>
Redirect I/O to socket.
Any input from clients connected to the socket is sent on the serial port as if entered at the
terminal where tio is running (except that ctrl-t sequences are not recognized), and any input
from the serial port is multiplexed to the terminal and all connected clients.
Sockets remain open while the serial port is disconnected, and writes will block.
Various socket types are supported using the following prefixes in the socket field:
unix:<filename> Unix Domain Socket (file)
inet:<port> Internet Socket (network)
inet6:<port> Internet IPv6 Socket (network)
If port is 0 or no port is provided default port 3333 is used.
At present there is a hardcoded limit of 16 clients connected at one time.
--rs-485
Enable RS-485 mode.
--rs-485-config <config>
Set the RS-485 configuration using the following key or key value pair format in the configuration
field:
RTS_ON_SEND=value Set logical level (0 or 1) for RTS pin when sending
RTS_AFTER_SEND=value Set logical level (0 or 1) for RTS pin after sending
RTS_DELAY_BEFORE_SEND=value Set RTS delay (ms) before sending
RTS_DELAY_AFTER_SEND=value Set RTS delay (ms) after sending
RX_DURING_TX Receive data even while sending data
If defining more than one key or key value pair, they must be comma separated.
--alert none|bell|blink
Set alert action on connect/disconnect.
It will sound the bell once or blink once on successful connect. Likewise it will sound the bell
twice or blink twice on disconnect.
Default value is "none".
--mute
Mute tio messages.
--script <string>
Run script from string.
--script-file <filename>
Run script from file with filename.
--script-run once|always|never
Run script on connect once, always, or never.
Default value is "always".
--exec <command>
Execute shell command with I/O redirected to device
-v, --version
Display program version.
-h, --help
Display help.
KEY COMMANDS
In session, all key strokes are forwarded to the serial device except the following key sequence: a
prefix key (default: ctrl-t) followed by a command key. These sequences are intercepted as key commands:
ctrl-t ? List available key commands
ctrl-t b Send serial break (triggers SysRq on Linux, etc.)
ctrl-t c Show configuration (baudrate, databits, etc.)
ctrl-t e Toggle local echo mode
ctrl-t f Toggle log to file
ctrl-t F Flush data I/O buffers (discard data written but not transmitted and data received but
not read)
ctrl-t g Toggle serial port line
ctrl-t i Toggle input mode
ctrl-t l Clear screen
ctrl-t L Show line states (DTR, RTS, CTS, DSR, DCD, RI)
ctrl-t m Change mapping of characters on input or output
ctrl-t o Toggle output mode
ctrl-t p Pulse serial port line
ctrl-t q Quit
ctrl-t r Run script
ctrl-t R Execute shell command with I/O redirected to device
ctrl-t s Show TX/RX statistics
ctrl-t t Toggle line timestamp mode
ctrl-t v Show version
ctrl-t x Send file using the XMODEM-1K or XMODEM-CRC protocol (prompts for file name and protocol)
ctrl-t y Send file using the YMODEM protocol (prompts for file name)
ctrl-t ctrl-t Send ctrl-t character
SCRIPT API
Tio suppots Lua scripting to easily automate interaction with the tty device.
In addition to the standard Lua API tio makes the following functions available:
expect(string, timeout)
Expect string - waits for string to match or timeout before continuing. Supports regular
expressions. Special characters must be escaped with '\\'. Timeout is in milliseconds, defaults to
0 meaning it will wait forever.
Returns 1 on successful match, 0 on timeout, or -1 on error.
On successful match it also returns the match string as second return value.
read(size, timeout)
Read from serial device. If timeout is 0 or not provided it will wait forever until data is ready
to read.
Returns number of bytes read on success, 0 on timeout, or -1 on error.
On success, returns read string as second return value. Also emits a single timestamp to stdout
and log file per options.timestamp and options.log.
read_line(timeout)
Read line from serial device. If timeout is 0 or not provided it will wait forever until data is
ready to read.
Returns number of bytes read on success, 0 on timeout, or -1 on error.
On success, returns the string that was read as second return value. Also emits a single timestamp
to stdout and log file per options.timestamp and options.log.
write(string)
Write string to serial device.
Returns number of bytes written on success or -1 on error.
send(file, protocol)
Send file using x/y-modem protocol.
Protocol can be any of XMODEM_1K, XMODEM_CRC, YMODEM.
tty_search()
Search for serial devices.
Returns a table of number indexed tables, one for each serial device found. Each of these tables
contains the serial device information accessible via the following string indexed elements "path",
"tid", "uptime", "driver", "description".
Returns nil if no serial devices are found.
set{line=state, ...}
Set state of one or multiple tty modem lines.
Line can be any of DTR, RTS, CTS, DSR, CD, RI
State is high, low, or toggle.
sleep(seconds)
Sleep for seconds.
msleep(ms)
Sleep for milliseconds.
exit(code)
Exit with exit code.
CONFIGURATION FILE
Options can be set via configuration file using the INI format. tio uses the configuration file first
found in the following locations in the order listed:
$XDG_CONFIG_HOME/tio/config
$HOME/.config/tio/config
$HOME/.tioconfig
Labels can be used to group settings into named configuration profiles which can be activated from the
command-line when starting tio.
tio will try to match the user input to a configuration profile by name or by pattern to get the TTY
device and other options.
Options without any label change the default options.
Any options set via command-line will override options set in the configuration file.
The following configuration file options are available:
pattern Pattern matching user input. This pattern can be an extended regular expression
with a single group.
device TTY device to open. If it contains a "%s" it is substituted with the first group
match.
baudrate Set baud rate
databits Set data bits
flow Set flow control
stopbits Set stop bits
parity Set parity
output-delay Set output character delay
output-line-delay Set output line delay
line-pulse-duration Set line pulse duration
no-reconnect Do not reconnect
log Enable log to file
log-file Set log filename
log-directory Set log directory path in which to save automatically named log files.
log-append Append to log file
log-strip Enable strip of control and escape sequences from log
local-echo Enable local echo
timestamp Enable line timestamp
timestamp-format Set timestamp format
timestamp-timeout Set timestamp timeout
map Map characters on input or output
color Colorize tio text using ANSI color code ranging from 0 to 255
input-mode Set input mode
output-mode Set output mode
socket Set socket to redirect I/O to
prefix-ctrl-key Set prefix ctrl key (a..z or 'none', default: t)
rs-485 Enable RS-485 mode
rs-485-config Set RS-485 configuration
alert Set alert action on connect/disconnect
mute Mute tio messages
script Run script from string
script-file Run script from file
script-run Run script on connect
exec Execute shell command with I/O redirected to device
It is possible to include the content of other configuration files using the include directive like so:
"[include <file>]".
CONFIGURATION FILE EXAMPLES
To change the default configuration simply set options like so:
[default]
baudrate = 9600
databits = 8
parity = none
stopbits = 1
color = 10
line-pulse-duration = DTR=200,RTS=400
Named configuration profiles can be added via labels:
[rpi3]
device = /dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTGQVXBL-if00-port0
baudrate = 115200
color = 11
Activate the configuration profile by name:
$ tio rpi3
Which is equivalent to:
$ tio -b 115200 -c 11 /dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTGQVXBL-if00-port0
A configuration profile can also be activated by its pattern which supports regular expressions:
[usb-devices]
pattern = ^usb([0-9]*)
device = /dev/ttyUSB%m1
baudrate = 115200
Activate the configuration profile by pattern match:
$ tio usb12
Which becomes equivalent to:
$ tio -b 115200 /dev/ttyUSB12
It is also possible to combine use of configuration profile and command-line options. For example:
$ tio -l -t usb12
EXAMPLES
Typical use is without options:
$ tio /dev/ttyUSB0
Which corresponds to the commonly used default options:
$ tio -b 115200 -d 8 -f none -s 1 -p none /dev/ttyUSB0
It is recommended to connect serial TTY devices by ID:
$ tio /dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTGQVXBL-if00-port0
Using serial devices by ID ensures that tio automatically reconnects to the correct serial device if it
is disconnected and then reconnected.
Redirect serial device I/O to Unix file socket for scripting:
$ tio -S unix:/tmp/tio-socket0 /dev/ttyUSB0
Then, to issue a command via the file socket simply do:
$ echo "ls -la" | nc -UN /tmp/tio-socket0 > /dev/null
Or use the expect command to script an interaction:
#!/usr/bin/expect -f
set timeout -1
log_user 0
spawn nc -UN /tmp/tio-socket0
set uart $spawn_id
send -i $uart "date\n"
expect -i $uart "prompt> "
send -i $uart "ls -la\n"
expect -i $uart "prompt> "
It is also possible to use tio's own simpler expect/send script functionality to e.g. automate logins:
$ tio --script 'expect("login: "); write("root\n"); expect("Password: "); write("root\n")'
/dev/ttyUSB0
Redirect device I/O to network file socket for remote TTY sharing:
$ tio --socket inet:4444 /dev/ttyUSB0
Then, use netcat to connect to the shared TTY session over network (assuming tio is hosted on IP
10.0.0.42):
$ nc -N 10.0.0.42 4444
Pipe command to the serial device:
$ echo "ls -la" | tio /dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTGQVXBL-if00-port0
Pipe command to serial device and wait for line response within 1 second:
$ echo "*IDN?" | tio /dev/ttyACM0 --script "expect('\r\n', 1000)" --mute
Likewise, to pipe data from file to the serial device:
$ cat data.bin | tio /dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTGQVXBL-if00-port0
Map NL to CR-NL on input from device and DEL to BS on output to device:
$ tio --map INLCRNL,ODELBS /dev/ttyUSB0
Enable RS-485 mode:
$ tio --rs-485 --rs-485-config=RTS_ON_SEND=1,RX_DURING_TX /dev/ttyUSB0
Manipulate DTR and RTS lines upon first connect to reset connected microcontroller:
$ tio --script "set{DTR=high,RTS=low}; msleep(100); set{RTS=toggle}" --script-run once
/dev/ttyUSB0
WEBSITE
Visit https://tio.github.io
AUTHOR
Maintained by Martin Lund <martin.lund@keep-it-simple.com>.
tio 3.9 2025-04-13 tio(1)